The challenge for the development of ion and Hall thrusters using alternative propellants is to realize a corrosion-resistant 100mA-class cathode. As a candidate, a thermionic cathode using lanthanum hexaboride (LaB6) as an electron emitter has been studied. One of the disadvantages of thermionic cathodes is high power consumption due to radiation heat loss. In this study, a LaB6 thermionic cathode with Multilayer insulator (MLI) was developed, and thermal performance was evaluated by emission spectroscopy and thermal model analysis. As a result, a LaB6 temperature of 1802K was achieved with a heating power of 102 W. A comparison of the thermal model calculations, which were in good agreement with the experimental results, showed that MLI reduced the heating power by up to 77%. The thermal model analysis suggested that the performance of 38W of heating power and 100mA of thermionic current could be achieved by increasing the number of MLI layers and reducing the gaps.
